1. Field of the Invention
This invention relates to a large aperture, wide-angle, high performance zoom lens system whose magnification can be changed over a wide range, and more particularly to such a zoom lens system especially suitable for a TV camera.
2. Description of the Prior Art
A zoom lens system for a TV camera is required to be large both in aperture and angle of view, to be small in size, to be able to change its magnification over a wide range, to be able to take a closeup at a short distance and to be well corrected in aberrations. There have been developed various zoom lens systems to meet such requirements.
For example, in the zoom lens system disclosed in U.S. Pat. No. 4,245,891, a corrective lens group having a weak refracting power is disposed on the object side of a concave lens group which forms a zoom lens group together with a convex lens group and distortion of the zoom lens system is compensated for by moving the corrective lens group when zooming.
However in the zoom lens system, it is difficult to effectively suppress fluctuation in coma with change in the zooming position of the lens system though fluctuation in distortion can be effectively suppressed.
In the zoom lens system disclosed in U.S. Pat. No. 4,560,254, the zoom lens group consists of a concave lens group and a pair of convex lens groups, and when zooming, the convex lens groups are moved so that the distance therebetween is changed so as to shorten the distance of movement of the concave lens group, whereby fluctuation in distortion is effectively compensated for.
Also in the zoom lens system, though fluctuation in distortion can be effectively suppressed, it is difficult to effectively suppress fluctuation in other aberrations especially coma.
Further when the aperture and the angle of view are enlarged, the size of the lens system is reduced, the variable range of magnification is widened and the closeup distance is shortened in the conventional zoom lens systems, fluctuation in coma and the like becomes too large.